Clarified comment

quad/src/computation_graph/computation_graph.c

@@ -186,7 +186,8 @@ double graph_get_output(const struct computation_graph *graph, int node_id, int
 /*
  * Assumptions: The node passed in is a valid ID (should be checked before passing)
  * and all node sources are either valid node-output pairs, or the source node ID == -1
- * This function does not check those assumptions for speed
+ * These constraints should be satisfied by using the graph_set_source function, so long as
+ * a valid node ID is passed in to the first call of this function
 */
 void graph_compute_node_rec(struct computation_graph *graph, int node_id, int depth) {
     if (depth >= GRAPH_MAX_DEPTH) {